1. Field of the Invention
This invention relates to protective caps for couplings, and other hose end fittings used in liquid transport and more particularly to a protective safety cap to protect couplings and hose fittings from damage, prevent electric buildup and discharge, protect from vapor discharge and protect the operator's hand.
2. Description of Related Art
Cam and groove couplings and hose fittings are used in the liquid delivery industry and in many liquid transport applications. A circumferential groove on the male fitting mates with two articulating cams inside the female fitting. The cams typically have elongated cam arms that are rotated out to release the fittings and inward against the outside of the female fitting where cam lobes engage in the groove of the male fitting.
Both the male fitting and the cam arms on the female fitting are subject to damage. Male hose end fittings are especially vulnerable to dropping, abrasion and strikes from heavy objects that will deform or break the fitting.
Damage to female fittings will deform or disable the cams or make it impossible to make a liquid tight seal between fittings. As a result, considerable time is lost trying to operate a damaged fitting. Replacing fittings can be expensive and very inconvenient to operations. Threaded fittings and victaulic fittings are also subject to damage from strikes, dropping and handling.
In addition, hose trays and tubes used to carry hoses on trucks can be damaged by the fittings when hoses are loaded and unloaded and during transport. Metal fittings are typically used for flammable liquids to avoid build up of static electricity.
Dust caps for male and female cam and groove fittings are known in the art. A conventional male dust cap 10 is shown in FIG. 1. The cylindrical body 12 is usually hollow and has an insertion end 14 that may have a tapered lip. A circumferential groove 16 cooperates with the cam of the female fitting. The shoulder 18 of the outside end is typically the same diameter as the inner diameter of the fitting to be protected. A tab 20 on the outside end of dust cap 10 has an aperture 20 that will accommodate a split ring 24 or keeper chain.
In use operators have to grasp the ring 24 with one finger or tab 20 with two fingers to remove the dust cap from the female fitting. This can be difficult with gloved hands and inside hose tubes. Frequent use wears out the fingers of gloves. Operators also use the ring to move the end of hoses. Movement of fluid in the hose can cause the ring to put extreme stress on the finger. If tab 20 breaks, the dust cap is useless and must be discarded. Other dust caps have a lip around the outside end of the dust cap that must be grasped by the fingers.
Because the diameter of shoulder 18 is less than the outer diameter of the fitting to be protected, it affords no protection if the fitting is struck or dropped, for example on the end of a hose.
If there is pressure built up in the capped hose, releasing the dust cap can result in vapor spray or forcible ejection of the dust cap. Some female fittings are equipped with interlocking rings on the cam arms that cooperate with a lock placed through aperture 22 or ring 24 to allow the dust cap to be locked in place to prevent unauthorized removal or vandalism.
FIG. 2 illustrates a partial cutaway view of a conventional female cap 30 for a cam and groove male fitting. Body 32 is cylindrical with opening 34 accommodating the male fitting. Note there is typically no skirt with an extended diameter at opening 34. Body 32 has a pair of cam ears 36 with apertures 38 that support rotating cam arms 40 on pins 42 in apertures 38. Rotating cam arms 40 have cam lobe 44 that extends through opening 46 in body 32 to interact with the groove in the male fitting. The ends of rotating cam arms 40 are shown with rings 48. To engage with a male fitting, a pressure of up to 35 pounds per square inch must be exerted with the palm of the hand against cam arm 40. Frequent use results in bruising of the hand.
Body 32 is closed at the top end with tab 50 having aperture 52. Rings 48 can cooperate with a lock through aperture 52 to secure cam arms 40 in the locked position. Note that cam arms 40 are exposed when in the locked position and are subject to damage if struck, dropped or dragged on pavement. The arms also cause damage to hose tubes and trays during transport. A gasket ring 54 is positioned inside body 32 to seal the end of the male fitting.
In use, the operator either has to grasp body 32, tab 50 or ring 48 with a finger to remove the cap. This can be difficult for large diameter fittings, inside hose tubes and with gloved hands. Manipulating the hose end using ring 48 can result in injuries to the finger or hand.
Dust caps for volatile or flammable service, such as in the petroleum industry are preferably made of metal such as aluminum so they dissipate any static charge that may develop during handling or connection of hoses or during pumping of fluid. The metal caps can themselves cause damage when striking other fittings, hose trays and tubes. Hard plastic dust caps are available for non-flammable liquid duty.